This invention relates to a differential pressure limiting valve with a valve casing defining a valve cavity and port means for a pressure medium. The valve casing has bearing bores and a valve seat. A cone shaped valve body cooperates with the valve seat and is axially slideable in the cavity of the valve casing.
Pressure limiting valves such as pressure relief valves, safety valves, cut-off valves, etc. are valves which open an exit cross sectional passage when a specified pressure is exceeded thereby preventing that the pressure, particularly in a hydraulic system, exceeds a pedetermined highest value. Differential pressure limiting valves are supposed to limit a pressure difference, for example, between the chambers of a piston drive cylinder.
Known types of differential pressure relief valves have not satisfactorily solved the problem of limiting the differential pressure to a value of zero. Particularly valves with a large flow volume have not satisfactorily solved this problem since the valve surfaces of the employed valves are not equal. The reason for this, among others, is attributable to the fact that for differential pressure limiting a preliminary controlling stage and a main controlling stage are required. Even the preliminary controlling stage itself requires a differential pressure for its actuation. Throttling devices in the main controlling stage produce an additional differential pressure so that undesired response differential pressures necessarily result. When such differential pressure limiting valves are used, for example, on the loading cylinders of testing equipment, turn-on impulses may occur at the specimens being tested which either damage the specimen or affect the test result.